1. Field of the Invention
The present invention relates to an image recognition device, an image recognition method, and an image recognition program suited for use in a face authentication process on, for example, a photographed image.
2. Description of the Related Art
Conventionally, a face authentication process on a photographed image is performed by identifying the face of which of persons registered in advance the face of a person present in the photographed image corresponds to. Various image recognition techniques are employed for this face recognition. Basically, in general, as disclosed in Japanese Patent Application Laid-Open No. 2000-306095, there is a technique for (1) performing face detection for extracting an image corresponding to a face part of a person from each of photographed images, (2) comparing the detected image corresponding to the face part with each of a plurality of face images registered (stored) in advance, and (3) searching the face image a matching degree of which is equal to or higher than a standard.
To improve accuracy of the face authentication process, that is, to improve accuracy of the face recognition process including object identification, it is desirable to store a plurality of types of face images in varied states as recognition candidates for each of registered persons in advance. However, if the number of recognition candidates per person increases, then processing load required for the face recognition disadvantageously increases and it disadvantageously takes a longer time for the face recognition process. That is, in a case of a device having a fixed processing capability, authentication accuracy and authentication speed are in a tradeoff relationship. Particularly if the face recognition process is repeatedly performed, it is disadvantageously difficult to simultaneously satisfy authentication accuracy and authentication speed.